FIGURE 6-1. BRUSH WINDROWS ON ISLAND JANET. This aerial view, looking almost due north, shows the extent and direction of windrowing efforts. Brush cover on this portion of the island was heavier and more complete than on the other half of this island, or any of the other ground zero islands. (Fall 1977) Also different from both the Test Grid model and the west model was the variogram for the 50 m Janet data. The anisotropy was much less pronounced, and it appeared even the mathematical form of the model might have changed. These changes apparently resulted from the windrow method used to devegetate Janet (Figure 6-1 and Section 6.5.2). In the process of bulldozing the vegetation into east-west windrows, the surface soil was mixed, primarily in a north-south direction along the bulldozer tracks, thereby reducing the anisotropy that was caused by wind effect. Measured surface TRU activity also decreased, partly from mixing and partly because some of the surface soil was inadvertently scraped up and deposited in and under the windrow. The soil under the windrows was eventually removed as part of the surface cleanup (see Section 7.5.2). Because it was not clear what model would best fit the raw variogram on the 50 m data, two different models were fitted, then tested to determine which was better. One model explicitly accounts for the effect of windrowing while tne other ignores the windrows. The latter model was the same mathematical form as the Test Grid and west area models, but the former model has an entirely different form. 161